Glass/resin composite structure and method for manufacturing same

ABSTRACT

A composite structure with high pressure resistance that is suitable for a flow channel is produced by reducing the number of components while maintaining the excellent chemical resistance and high stress tolerance inherent to a glass substrate and a resin substrate. A glass substrate surface is modified with a hydrolyzable silicon compound, and the glass substrate is brought into contact with the resin substrate. Subsequently, the contact surface between the glass substrate and the resin substrate is heated to a temperature from the glass transition temperature to the pyrolysis temperature of the resin substrate, eliminating gaps between the glass substrate and the resin substrate to bring them into close contact with each other, and causing chemical binding or anchor effects between the glass substrate and the resin substrate via the hydrolyzable silicon compound. Thus, the glass substrate and the resin substrate are firmly fixed to each other.

TECHNICAL FIELD

The present invention relates to a composite structure of a glasssubstrate bonded to a resin substrate that is suitable for a flowchannel and a method for producing the same.

BACKGROUND ART

Use of a wide variety of solvents is required for general-purpose liquidanalyzers represented by flow injection analyzers and liquidchromatography apparatuses, and, in general, flow channels in suchapparatuses are required to have excellent chemical resistance and highpressure resistance. As materials that satisfy such requirements,organic materials, such as super engineering plastics includingpolyether ether ketone resin (hereafter abbreviated as “super enpla”),and inorganic materials, such as silica glass and stainless steel, areknown. In particular, a combination of silica glass with polyether etherketone resin is suitable for a material constituting a flow cell forphotometric analysis because of properties of silica glass, such as highlight permeability in an extensive wavelength region, excellent chemicalresistance, and high stress tolerance, and properties of super enpla,such as excellent moldability and processability, excellent chemicalresistance, and high stress tolerance. Accordingly, various bondingtechniques have heretofore been attempted. The simplest method forbonding silica glass to resin comprises dissolving resin in a solvent,bringing liquefied resin into close contact with silica glass, andremoving the solvent by evaporation. In the case of a material such assuper enpla with excellent chemical resistance, however, there has beenno sufficient solubilizing solvent, and the method as described abovecould not be employed.

Accordingly, a method of bonding involving the use of an adhesive agentand a method of bonding via pressure bonding had been employed. Whenpolyether ether ketone resin is bonded to silica glass via the formermethod, for example, a method of bonding involving the use of anadhesive agent, such as epoxy-based resin or acrylic resin, isrecommended. In the case of the latter method, a method making use of aconfigurational change caused by volume expansion or contraction, suchas shrinkage fit or cooling fit, and a method of using a configurationalchange caused by plastic deformation involving the use of ferrules andnuts have been developed. As another method associated with plasticdeformation, a method of bonding comprising heating resin to its meltingpoint or higher, bringing the liquefied resin into close contact withsilica glass, and cooling the resultant to resolidify it is known.

As an attempt to allow silica glass to chemically bind to resin, amethod of bonding comprising forming membranes containing siloxanegroups on both silica glass and resin substrate surfaces via plasmapolymerization, and heating the substrates at a low temperature of 100°C. or lower so as to fix the membranes formed via plasma polymerizationto each other via polymerization of siloxane groups has been reported(Patent Document 1).

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP 4,337,935 B2

SUMMARY OF THE INVENTION Objects to be Attained by the Invention

According to a conventional technique, it was impossible to produce acomposite structure with high pressure resistance that would be suitablefor a flow channel by reducing the number of components whilemaintaining the excellent chemical resistance and high chemicalresistance inherent in silica glass and super enpla.

According to a method involving the use of an adhesive agent, in thecase of polyether ether ketone resin, for example, epoxy resin oracrylic resin at the bonded interface has low resistance to organicsolvents and acid-base solvents. This disadvantageously causes thechemical resistance of the entire composite structure to deteriorate,and chemical resistance of silica glass and polyether ether ketone resincannot be utilized.

According to a method employing pressure bonding, silica glasscomponents are damaged when high degrees of stress are applied. Thus,high stress cannot be applied, and pressure resistance disadvantageouslyremains as low as about several MPa. In addition, a method employingpressure bonding requires the use of an increased number of componentsin order to support the contact plane between the silica glass componentand the super enpla component. According to a method comprisingheat-melting super enpla so as to fuse the same to deposit it ontosilica glass, further, affinity at the interface between silica glassand super enpla is low, and silica glass and super enpla repel eachother. When super enpla is peeled from the glass as it shrinks at thetime of resolidification during the cooling process, gaps are formed atthe interface, and liquid leaks through such gaps.

In general, the surface tension between silica glass and super enpla ishigh. When both silica glass and super enpla are flat plates,accordingly, a configuration of super enpla is altered so as to minimizethe energy, and silica glass is brought into point-contact with superenpla, as shown in FIG. 24. The influence of lowered pressure resistancecaused thereby becomes significant when silica glass and super enpla arecylindrical tubes, as shown in FIG. 25. When a substance having affinityhigher than that of silica glass, such as resin of the same type orstainless steel, is provided around super enpla, in particular, superenpla shrinks toward the substance with higher affinity during theprocess of cooling. Thus, super enpla would be peeled from the silicaglass surface at an accelerated speed. While FIG. 25 shows an embodimentin which the outer cylindrical tube is made of super enpla and the innercylindrical tube is made of silica glass, the same phenomena wouldnaturally occur if the material constituting the outer cylindrical tubewere to be replaced with the material constituting the inner cylindricaltube. In order to avoid such phenomena, it is necessary to apply stressto the contact plane between super enpla and silica glass when superenpla is to be resolidified. However, this method involves pressurebonding and, accordingly, the problem described above remainsunresolved.

According to a method of allowing silica glass to chemically bind toresin by heating both materials at a low temperature of 100° C. orlower, as shown in FIG. 26, the substrates are brought intopoint-contact with each other due to irregularities on the substratesurface, gaps are formed at the interface, and pressure resistance islowered as a consequence. When a substrate is in a tubular form such asa cylindrical tube, as shown in FIG. 27, the substrates are brought intopoint-contact with each other because of gaps resulting from dimensionaltolerance caused at the time of processing, gaps are formed at theinterface, and pressure resistance is lowered as a consequence,disadvantageously. As with the case shown in FIG. 25, the same problemwould arise even if materials constituting the substrates were to bereplaced with each other.

Under the above circumstances, the present invention is intended toprovide a composite structure with high pressure resistance that issuitable for a flow channel while maintaining high chemical resistanceinherent in silica glass and super enpla and a method for producing thesame.

Means for Attaining the Objects

A method for producing the composite structure provided with a flowchannel and constituted of a glass substrate and a resin substrateaccording to the present invention comprises: a step of modifying aglass substrate surface with a hydrolyzable silicon compound; a step ofbringing the glass substrate into contact with the resin substrate; anda step of heating the contact plane between the glass substrate and theresin substrate to a temperature from the glass transition temperatureto the pyrolysis temperature of the resin substrate, eliminating gapsbetween the glass substrate and the resin substrate to bring them intoclose contact with each other, and causing chemical bonding and/oranchor effects between the glass substrate and the resin substrate viathe hydrolyzable silicon compound. According to a representativeembodiment, the glass substrate is a silica glass substrate, and theresin substrate is a super enpla substrate.

Preferably, the method of modification with a hydrolyzable siliconcompound is wet coating involving the use of a solution of ahydrolyzable silicon compound, and the hydrolyzable silicon compound isa silicon compound having an alkoxy group. Also, it is preferable thatthe contact plane between the silica glass substrate and the super enplasubstrate be heated to a temperature from the melting point to thepyrolysis temperature of the super enpla. The flow channel may beprovided inside the silica glass substrate or the super enpla substratein advance, or a flow channel may be formed when these substrates arebonded to each other.

The composite structure of the present invention is composed of theglass substrate bonded to the resin substrate in which a flow channel isprovided. On the contact plane between the glass substrate and the resinsubstrate, the angle of the end planes of the region at which the resinsubstrate is bonded to the interface is 0 degrees to 90 degrees.

Effects of the Invention

By heating the contact plane between the silica glass substrate and thesuper enpla substrate to the glass transition temperature or higher ofthe super enpla, super enpla is softened or liquefied, gaps between thesilica glass and the super enpla are eliminated, the silica glasssubstrate is brought into surface-to-surface contact with the superenpla substrate, and adhesion therebetween is improved as a consequence.In addition, chemical bonding takes place via a hydrolyzable siliconcompound between the silica glass and the super enpla at a hightemperature of the glass transition temperature or higher, and affinitybetween the silica glass and the super enpla is improved as aconsequence. Further, anchor effects arise as the softened or liquefiedsuper enpla enters into the hydrolyzable silicon compound, and frictionbetween the silica glass and the super enpla is improved. Thus, thecomposite structure can achieve high-pressure resistance. As thesecondary effects, super enpla forms a convex configuration againstsilica glass on the end plane of the region in which silica glassadheres to super enpla, the effective area of adhesion is increased, andstress concentration is thereby relieved. Thus, pressure resistance isimproved. According to the process of the present invention, sucheffects can be achieved in a single step, and the number of componentsand the number of steps can be minimized.

Objectives, constitutions, and effects other than those described aboveare demonstrated in the embodiments described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a process for producing a composite structure provided witha flow channel according to an embodiment of the present invention.

FIG. 2 shows a process for producing a composite structure provided witha flow channel according to an embodiment of the present invention.

FIG. 3 schematically illustrates the behavior of the adhesion planebetween silica glass and super enpla in the steps of heating and coolingaccording to the present invention.

FIG. 4 illustrates the angle of the end plane of a region in which superenpla is bonded to silica glass with respect to the adhesion planeaccording to the present invention.

FIG. 5 schematically illustrates the behavior of the adhesion planebetween silica glass and super enpla in the steps of heating and coolingaccording to a conventional technique.

FIG. 6 illustrates the angle of the end plane of a region in which superenpla is bonded to silica glass with respect to the adhesion planeaccording to a conventional technique.

FIG. 7 schematically illustrates the behavior of a cross section of theadhesion plane of silica glass and super enpla in the steps of heatingand cooling according to the present invention.

FIG. 8 shows a perspective view of the composite structure provided witha flow channel according to an embodiment of the present invention.

FIG. 9 shows a cross-sectional view of the composite structure providedwith a flow channel according to an embodiment of the present invention.

FIG. 10 shows an illustrative view showing a process for producing thecomposite structure provided with a flow channel according to anembodiment of the present invention.

FIG. 11 shows a perspective view of the composite structure providedwith a flow channel according to an embodiment of the present invention.

FIG. 12 shows a perspective view of the composite structure providedwith a flow channel according to an embodiment of the present invention.

FIG. 13 shows a cross-sectional view of the composite structure providedwith a flow channel according to an embodiment of the present invention.

FIG. 14 shows a perspective view of the composite structure providedwith a flow channel according to an embodiment of the present invention.

FIG. 15 shows a perspective view of the composite structure providedwith a flow channel according to an embodiment of the present invention.

FIG. 16 shows a cross-sectional view of the composite structure providedwith a flow channel according to an embodiment of the present invention.

FIG. 17 shows a perspective view of the composite structure providedwith a flow channel according to an embodiment of the present invention.

FIG. 18 shows a cross-sectional view of the composite structure providedwith a flow channel according to an embodiment of the present invention.

FIG. 19 shows a perspective view of the composite structure providedwith a flow channel according to an embodiment of the present invention.

FIG. 20 shows a cross-sectional view of the composite structure providedwith a flow channel according to an embodiment of the present invention.

FIG. 21 schematically shows an experimentation system of the pressureresistance test according to the present invention.

FIG. 22 shows the results of the pressure resistance tests of thecomposite structure provided with a flow channel according to aconventional technique and according to the present invention.

FIG. 23 shows the exterior of the composite structure provided with aflow channel according to an embodiment of the present invention.

FIG. 24 illustrates the problem of bonding between silica glass andsuper enpla in a planar form according to a conventional technique.

FIG. 25 illustrates the problem of bonding between silica glass andsuper enpla in a cylindrical form according to a conventional technique.

FIG. 26 illustrates the problem of bonding between silica glass andsuper enpla in a planar form according to another conventionaltechnique.

FIG. 27 illustrates the problem of bonding between silica glass andsuper enpla in a cylindrical form according to another conventionaltechnique.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Hereafter, embodiments of the present invention are described withreference to the drawings.

In the method of production according to the present invention, a silicaglass substrate may be a compound mainly composed of silicon that canchemically bind to a hydrolyzable silicon compound. Preferable examplesinclude synthetic silica glass, fused-silica glass, borosilicate glass,and soda glass having excellent light permeability. According to thepresent invention, a super enpla substrate is composed of a materialhaving low affinity with silica glass in a softened or liquefied state;that is, a material exhibiting high surface tension between the silicaglass and the super enpla. Polyallyl ether ketone-based resins, and,typically, polyether ether ketone resin, polyether ketone resin,polyether ketone ketone resin, polyether nitrile resin, and other resinsare preferable. Polysulfone-based resins, such as polysulfone resin,polyphenylene sulfide resin, polyether sulfone resin, andpolyphenylsulfone resin, polyimide resins, or polyamide-based resins maybe, for example, polyimide-based resin, polyetherimide resin, polyamideresin, or polyamide imide resin. While the engineering plasticsdescribed above are preferable in order to sufficiently achieve theeffects of the present invention, other general-purpose plastics, suchas polycarbonate resin, acrylic resin, epoxy resin, or fluorine-basedresin, such as polytetrafluoroethylene resin orpolytetrafluoroethylene-polyhexafluoropropylene resin, may be used.

In the method of production according to the present invention, thesilica glass substrate surface is first modified with a hydrolyzablesilicon compound. A hydrolyzable silicon compound may be a siliconcompound comprising an alkoxy group, and an alkoxy group preferably hasan alkyl group, such as a methoxy, ethoxy, propoxy, or butoxy group. Ahydrolyzable silicon compound may be a monomer, such astetraethoxysilane, or a polymer thereof, such as a polytetraethoxysilanecompound. A polymer is less likely to undergo self-polymerization, it ismore stable, and it is easier to handle, in comparison with a monomer.Thus, a polymer is preferable. A preferable solvent for a hydrolyzablesilicon compound is less likely to undergo self-polymerization, and analkyl alcohol having a number of carbon atoms that is the same as orclose to that of an alkyl group in the alkoxy group is desirable. In thecase of a polytetraethoxysilane compound, for example, a solvent ispreferably ethanol, propyl alcohol, isopropyl alcohol, or butanol.

The silica glass substrate surface may be coated with a solutioncontaining a hydrolyzable silicon compound by a general wet coatingtechnique. Examples of preferable techniques include dip coating, spincoating, and spray coating, so that membrane thickness can be regulated.Post-coating treatment is preferably a technique that modifies thesubstrate surface while maintaining hydrolyzability to a considerableextent, as described below. In the case of a polytetraethoxysilanecompound that is a polymer, for example, dehydration may be carried outat room temperature. In contrast, it is necessary that a monomer (i.e.,tetraethoxysilane) be subjected to pre-treatment at high temperature(100° C. to 200° C.) after coating, in order to form a membrane of acertain thickness. Thus, a hydrolyzable silicon compound is chemicallybound to and made to tightly adhere to the silica glass substratesurface. In addition to wet coating, the CVD or PVD method may beemployed.

The silica glass substrate modified with the hydrolyzable siliconcompound in the manner described above is brought into contact with thesuper enpla substrate, and the contact plane between the silica glasssubstrate and the super enpla substrate is heated to the glasstransition temperature or higher of the super enpla substrate. Theheating temperature may be the glass transition temperature or higher atwhich the super enpla substrate is softened and adheres more tightly tothe silica glass substrate to the pyrolysis temperature. The heatingtemperature is preferably in a range from the melting point at which thesuper enpla substrate is liquefied to the pyrolysis temperature. Byheating the super enpla substrate to its glass transition temperature orhigher, softened or liquefied resin enters into irregular gaps at theinterface between the substrates, and the contact between the substratesis improved from point contact to surface-to-surface contact. In suchcase, the hydrolyzable silicon compound modifying the silica glasssurface is hydrolyzed by thermal energy at a temperature higher than theglass transition temperature, and it is chemically bound to the superenpla substrate. Thus, affinity between these substrates issignificantly improved, and the substrates are tightly adhered to eachother.

The hydrolyzable silicon compound forms a structure having micro-gaps ofseveral angstroms (Å) to several nanometers (nm) on the silica glasssurface. Thus, the softened or liquefied super enpla substrate entersinto the gaps, anchor effects are exerted and friction is enhanced to asignificant extent, and the substrates adhere more tightly to eachother. The term “anchor effects” used herein refers to effects resultingwhen mechanical strength is enhanced as a result of softened orliquefied resin entering into micro-gaps on the substrate surface andhardening.

Heating may be carried out by heating the entire structure with the useof, for example, an incubator or electric furnace. When a part of thestructure is to be topically heated, for example, heat is transferredfrom the silica glass substrate side using a hot plate heated whileapplying an electric current, so as to heat the contact plane betweenthe silica glass substrate and the super enpla substrate. Alternatively,a heating wire capable of heating to a high temperature with theapplication of an electric current may be provided in the vicinity ofthe contact plane between the silica glass substrate and the super enplasubstrate in advance and heat may be applied later. Further, aheat-transfer member capable of heating via electromagnetic induction,such as stainless steel, may be provided in the vicinity of the contactplane between the silica glass substrate and the super enpla substrate,and heat may be applied with the aid of the heat-transfer member byso-called induction heating by which a high-frequency magnetic field ofseveral tens to several hundreds of kHz is applied. In addition, theadhesion plane may be selectively heated by ultrasonic waves, forexample. Alternatively, induction heating using a high frequency ofseveral tens to several hundreds of MHz that allow the super enplasubstrate to produce heat may be carried out. Heating may be carried outby supplying a certain quantity of heat or instantaneously supplying athermal pulse. When the heating temperature is from the glass transitiontemperature to the melting point (from the glass transition temperatureto the pyrolysis temperature in case of a material for which there is nomelting point), it is preferable that stress be applied to a regionbetween the silica glass substrate and the super enpla simultaneouslywith heating, in order to improve the adhesion strength. Super enpla maybe cooled naturally or forcibly when it is to be resolidified.

In the following examples, the composite structure composed of a silicaglass substrate and a super enpla substrate and provided with a flowchannel according to the present invention and the method for producingthe same are described. In the following examples, a representativesuper enpla; i.e., polyether ether ketone resin, was used.

FIG. 1 and FIG. 2 each show a composite tubing provided with a flowchannel according to an embodiment of the present invention. A compositetubing is constituted by a first cylindrical tube 301 made of polyetherether ketone resin and a second cylindrical tube 302 made of silicaglass having an outer diameter that is less than the inner diameter ofthe first cylindrical tube. With the use of a solution 303 containing ahydrolyzable silicon compound, as shown in FIG. 1, the secondcylindrical tube 302 was modified with a hydrolyzable silicon compound304 via dip coating by soaking the second cylindrical tube 302 in thesolution and raising the same from the solution. As shown in FIG. 2, thesecond cylindrical tube 302 was then inserted into the first cylindricaltube 301, and the resultant was heated to a temperature from the glasstransition temperature (143° C.) to the pyrolysis temperature (450° C.)of the polyether ether ketone resin using a heating wire 305 in a formcapable of covering the contact plane between the first cylindrical tubeand the second cylindrical tube (e.g., a circular or C-shaped form), soas to produce a composite tubing in which the surfaces to be bonded weretightly adhered to each other. In such a case, the heating temperatureis preferably adjusted between the melting point (343° C.) and thepyrolysis temperature (450° C.) of polyether ether ketone resin toenhance the fluidity, thereby increasing the area of surface-to-surfacecontact between the substrates.

As shown in FIG. 3, polyether ether ketone resin that is heated to atemperature equivalent to or higher than its melting point is softenedor liquefied and then it adheres to the silica glass. Such polyetherether ketone resin adheres tightly to the silica glass via chemicalbonding and anchor effects when it is resolidified. Thus, peeling thatoccurs according to a conventional technique can be prevented. In thisprocess, polyether ether ketone resin tends to shrink toward its center,and the adhesion plane between the polyether ether ketone resin and thesilica glass is tightly bonded. Accordingly, the polyether ether ketoneresin shrinks in a manner such that it is dragged to the adhesion planebetween the resin and the silica glass. As a result, as shown in FIG. 3,the end plane of a region in which the polyether ether ketone resin isbonded to the silica glass forms a configuration such that the polyetherether ketone resin wets the silica glass. More specifically, as shown inFIG. 4, the contact plane between silica glass and polyether etherketone resin is designated as the standard plane, and the angle (θ)formed by the end plane of a region in which the polyether ether ketoneresin is bonded to the silica glass with respect to the standard planeis from 0 degrees to 90 degrees (hereafter referred to as “convexconfiguration” for the convenience of explanation).

According to a conventional technique, however, a configuration suchthat the polyether ether ketone resin repels the silica glass is formedbecause of low affinity between the polyether ether ketone resin and thesilica glass, as shown in FIG. 5. More specifically, as shown in FIG. 6,the contact plane between silica glass and polyether ether ketone resinis designated as the standard plane, and the angle (θ) formed by the endplane of a region in which the polyether ether ketone resin is bonded tothe silica glass with respect to the standard plane is from above 90degrees to 180 degrees (hereafter referred to as a “concaveconfiguration” for the convenience of explanation). In such a concaveconfiguration, the effective area of adhesion between the polyetherether ketone resin and the silica glass is decreased. In addition,stress is often concentrated at a single minute point in such a concaveconfiguration, which leads to breakage of components and then causesleakage of liquid. In the case of a convex configuration according tothe present invention, however, the effective area of adhesion betweenthe polyether ether ketone resin and the silica glass is increased, andstress is not concentrated at a particular single point, unlike theconcave configuration. Thus, pressure resistance is improved.

Accordingly, the first cylindrical tube 301 is tightly adhered to thesecond cylindrical tube 302 as shown in FIG. 7, no gap is formed at theinterface, and a composite tubing with pressure resistance higher thanthat achieved via pressure bonding can be achieved. The initial gapbetween the first cylindrical tube and the second cylindrical tube ispreferably as minute as possible prior to adhesion. From the viewpointof engagement of components and retention of a super enpla substrateconfiguration upon heating, the initial gap is preferably 1 μm to 500μm. According to a dip coating method, areas other than the contactplane between the first cylindrical tube and the second cylindrical tuberemain coated with hydrolyzable silicon compounds. By baking thecomposite structure (e.g., at 120° C. for 20 minutes) followingpreparation thereof, a remaining unreacted hydrolyzable silicon compoundcan be inactivated. Since the inactivated hydrolyzable silicon compoundhas a chemical structure very similar to that of the silica glasssubstrate, properties of the silica glass substrate would not bedamaged. It is deduced that the reaction between the polyether etherketone resin and the hydrolyzable silicon compound take place between anether, carbonyl, or phenyl group in the polyether ether ketone resin andan alkoxy group in the hydrolyzable silicon compound cleaved viahydrolysis.

In the case of super enpla other than polyether ether ketone resin, theglass transition temperature of, for example, polyphenylene sulfideresin is 85° C., the melting point thereof is 285° C., and the pyrolysistemperature thereof is 480° C. Also, the glass transition temperature ofa polyamide resin PA66 is 50° C., the melting point thereof is 265° C.,and the pyrolysis temperature thereof is 454° C. Accordingly, it isnecessary that the heating temperature be adequately adjusted, so thattemperatures thereof remain within the ranges described above.

This embodiment is useful when connecting a device that is connected toa polyether ether ketone resin tubing to another device that isconnected to a silica glass tubing. For example, this embodiment can beapplied when connecting a polyether ether ketone resin tubing to a flowcell composed of silica glass. It can also be applied to connect bothends of a glass capillary of a liquid chromatography apparatus or toconnect both ends of a glass capillary of a gas chromatographyapparatus.

The structure provided with a flow channel according to the presentinvention is preferably used as a flow cell for a liquid analyzer.Specifically, it is also preferably used as a flow cell for photometricanalysis in a flow injection analyzer or a liquid chromatographyapparatus. A flow cell for a liquid analyzer is required to have highpressure resistance. Accordingly, a mechanical fastening mechanism usinga screw or the like was necessary in the past, and the number ofcomponents was very large. According to the present invention, thenumber of components constituting a flow cell can be reduced, andpressure resistance superior to that attained by a conventionaltechnique can be achieved because of the plurality ofpressure-resistance-improving effects described above.

FIG. 8 and FIG. 9 each show a flow cell for a liquid analyzer accordingto an embodiment. FIG. 8 and FIG. 9 show a perspective view and across-sectional view of the same flow cell. This flow cell is composedof a cell body 801 made of polyether ether ketone resin and windowmaterials 802 and 803 made of silica glass. A flow channel 804 isprovided in advance inside the cell body 801. In the flow channel 804,in particular, a region of the flow channel opened in a directionperpendicular to the window materials 802 and 803 serves as an opticalpath through which light is transmitted. The window materials 802 and803 are modified with a hydrolyzable silicon compound 805 via dipcoating. Thereafter, as shown in FIG. 10, the cell body 801 is subjectedto thermal pressure bonding with the window materials 802 and 803 bysandwiching the same with heating plates 806 and 807 that had beenheated to a temperature equivalent to or higher than the melting pointof the polyether ether ketone resin via electric current heating. Insuch a case, the heating temperature is adjusted to a temperatureequivalent to or higher than the melting point of the polyether etherketone resin, so that the window materials 802 and 803 are tightlyadhered to the cell body 801, and a flow cell with high pressureresistance can be produced. In order to prevent the polyether etherketone resin from becoming deformed and the configuration of the flowchannel from being different from the initial configuration, also, it ispreferable that heating be carried out with the application of thermalpulses and that bonding be completed in as short a time period aspossible. FIG. 8 shows a cylindrical optical path. In order to suppressthe spatial spreading of the sample, the inner diameter of the crosssection thereof is preferably 0.05 mm to 2 mm. The length of the opticalpath in the cell body is preferably 0.1 mm to 20 mm. While a cell bodyprovided with a representative cylindrical optical path is inspected asa flow cell for a liquid analyzer in FIG. 8, an optical path may be inthe form of, for example, an ellipse tubing, polygonal tubing, ortapered cylindrical tubing.

As shown in FIG. 11, tubings 808 and 809 made of polyether ether ketoneresin may be bonded to the inlet and the outlet of the flow channel 804in the cell body 801 provided with the window materials as shown in FIG.8 in the manner described below. Areas in the vicinities of the contactplanes between the cell body and the tubings 808 and 809 are each heatedto a temperature equivalent to or higher than the melting point of thepolyether ether ketone resin using heating wires in a form capable ofcovering the tubings 808 and 809. The contact planes are allowed toliquefy and then naturally cooled to resolidify. Thus, the cell body isintegrated with the tubings 808 and 809. In order to facilitate bonding,it is preferable that the forms of the inlet and the outlet of the flowchannel 804 in the cell body 801 be modified in advance so as to fitwith the outer diameter of the tubing. In order to prevent the tubingsfrom clogging upon heating, commercially available tubings each composedof a polyimide-coated glass cylinder coated with polyether ether ketoneresin are preferably used as the tubings 808 and 809. As describedabove, a flow cell with the minimized number of components and highpressure resistance can be produced.

FIG. 12 and FIG. 13 each show a flow cell for a liquid analyzeraccording to another embodiment. FIG. 12 and FIG. 13 show a perspectiveview and a cross-sectional view of the same flow cell. This flow cell iscomposed of a cylindrical cell body 1201 made of silica glass, two-wayjoints 1202 and 1203 comprising flow channels 1204 and 1205 and made ofpolyether ether ketone resin, and tubings 1206 and 1207 made ofpolyether ether ketone resin. The cell body 1201 is modified with ahydrolyzable silicon compound 1208 via dip coating, and the two-wayjoints 1202 and 1203 are brought into contact with the two-way joints1202 and 1203. With the use of a heating wire in a shape capable ofcovering the interface between the two-way joints 1202 and 1203 and thecell body 1201, the structure is heated from the cell body 1201 side toa temperature equivalent to or higher than the melting point of thepolyether ether ketone resin. Thus, the cell body 1201 is tightlyadhered to the two-way joints 1202 and 1203. The tubings 1206 and 1207are heated to a temperature equivalent to or higher than the meltingpoint of the polyether ether ketone resin using a heating wire whilethey are kept in contact with the two-way joints 1202 and 1203, and aflow cell comprising the cell body 1201, the two-way joints 1202 and1203, and the tubings 1206 and 1207 tightly adhered to each other can beproduced.

This flow cell structure is used for analysis in a space with a microvolume in a liquid analyzer. Specifically, it is used for analysishaving priority in a reduction of a space in which the sample spreadsover sensitivity. Examples of detection methods include a method inwhich light is allowed to permeate vertically with respect to thedirection of liquid flow in a cylindrical tube and the absorbance ismeasured and a method in which excited light is applied and fluorescenceis received. For example, an inner diameter of a cylindrical tube ispreferably 1 μm to 1 mm so as to minimize the space in which the samplespreads. A cylindrical tube length is preferably 0.1 mm to 1 mm.

While a cylindrical tube is exemplified as a form of a cell body in FIG.12, a cell body may be a polygonal tube. When fluorescence analysis isperformed, in particular, it is necessary that the amount of lightexcited and fluorescence scattered be reduced. As shown in FIG. 14,accordingly, a cell body 1401 is preferably composed of a rectangulartube, so that the amount of light scattered is small.

FIG. 15 and FIG. 16 each show a flow cell for a liquid analyzeraccording to another embodiment. FIG. 15 shows a perspective view of aflow cell and FIG. 16 shows a cross-sectional view of a part of the flowcell shown in FIG. 15. This flow cell is composed of a cylindrical cellbody 1501 made of silica glass, three-way joints 1502 and 1503 providedwith flow channels 1504 and 1505 and made of polyether ether ketoneresin, tubings 1506 and 1507 made of polyether ether ketone resin, andoptical fibers 1508 and 1509 made of silica glass that can introduce thelight to be measured into the optical path inside the cell body 1501.After the cell body 1501 and the optical fibers 1508 and 1509 aremodified with a hydrolyzable silicon compound 1510 via dip coating, thecylindrical tube, the optical fibers, the polyether ether ketone resintubing, and the three-way joint are brought into contact with eachother. Heating wires capable of covering areas surrounding the contactplanes between each of the cylindrical tube, the optical fibers, and thepolyether ether ketone resin tubings and the three-way joints areprovided and the structure is heated to a temperature equivalent to orhigher than the melting point of the polyether ether ketone resin. Thus,components are integrated with each other. This flow cell structure hasan optical waveguide path in a liquid analyzer, and it is mainly usedfor absorbance and fluorescence analyses. An inner diameter of acylindrical cell tube is preferably 0.01 mm to 1 mm and a cylindricaltube length is preferably 0.5 mm to 1000 mm.

In general, a flow cell for a microchip that is extensively used foranalytical chemistry is made of a silica glass substrate or siliconeresin that can be bonded to each other. In order to produce a connectionfor a microchip using silica glass a glass substrate and a polyetherether ketone resin, however, available techniques were limited topressure bonding using a screw and the like. In addition, methods ofbonding a flow cell to an external tubing that have actually beenpracticed in the past were limited to a method involving pressurebonding using a screw and the like. According to such conventionaltechnique, disadvantageously, the number of components was large andpressure resistance was as low as about several MPa. However, thecomposite structure provided with a flow channel according to thepresent invention is capable of overcoming the disadvantages describedabove, and it is preferably used as a flow cell for a microchip.

FIG. 17 and FIG. 18 each show a flow cell for a microchip according toan embodiment of the present invention. FIG. 17 and FIG. 18 show aperspective view and a cross-sectional view of the same flow cell. Thisflow cell is composed of a first substrate 1701 made of silica glass, asecond substrate 1702 made of polyether ether ketone resin, and tubings1703 and 1704 made of polyether ether ketone resin. A flow channel 1705connected to the tubings 1703 and 1704 is provided in advance inside thefirst substrate 1701. After the first substrate 1701 is modified with ahydrolyzable silicon compound 1706 via dip coating, the first substrate1701 is brought into contact with the second substrate 1702. Thereafter,the contact plane between the first substrate 1701 and the secondsubstrate 1702 is heated to a temperature equivalent to or higher thanthe melting point of the polyether ether ketone resin from the firstsubstrate 1701 side using a plate electrically heated to a temperatureequivalent to or higher than the melting point of the polyether etherketone resin. The resultant is then naturally cooled to room temperatureto allow the second substrate 1702 to resolidify.

Subsequently, a heating wire capable of thermal pressure bonding isprovided in the vicinity of the contact plane between the firstsubstrate 1701 and the tubing 1703 or 1704 in the same manner as thatshown in FIG. 11, the contact plane is heated to a temperatureequivalent to or higher than the melting point of the polyether etherketone resin while pressing the heating wire against the tubing 1703 or1704, and the polyether ether ketone resin tubing is then naturallycooled to resolidify. Thus, a flow cell for a microchip comprisingsilica glass and polyether ether ketone resin tightly adhering to eachother can be produced.

The width of the flow channel 1705 according to this embodiment ispreferably 1 μm to 1 mm and the height of the flow channel is preferably1 μm to 1 mm Materials constituting the substrates of the structure maybe replaced with each other. In such a case, tubing is preferably madeof silica glass. While a cross section of the flow channel is in arectangular form in this embodiment, a cross section may be in acircular, elliptical, or polygonal form.

A flow cell for photometric analysis may be a composite structurecomprising a glass substrate provided with holes to be connected totubings, a polyether ether ketone resin substrate provided with a slotfor a flow channel, and another glass substrate superposed on top ofeach other, and a polyether ether ketone resin tubing is connectedthereto. FIG. 19 and FIG. 20 each show a flow cell according to suchembodiment. FIG. 19 and FIG. 20 show a perspective view and across-sectional view of the same flow cell. This flow cell is composedof first substrates 1901 and 1902 made of silica glass, a secondsubstrate 1903 made of polyether ether ketone resin, and tubings 1904and 1905 made of polyether ether ketone resin. In the same procedure asthat shown in FIG. 17, a silica glass surface is modified with thehydrolyzable silicon compound 1907, and a flow cell for a microchipcomprising silica glass and polyether ether ketone resin tightlyadhering to each other can be produced. Thus, light can permeate theflow cell, which enables absorbance analysis and fluorescence analysis.

While embodiments in which the number of components was minimized weredescribed above, for example, an electric heating member may constitutea part of a composite structure provided with a flow channel.

In order to confirm the effects of improved adhesion strength accordingto the present invention, the adhesion plane between the silica glassplate and the polyether ether ketone resin plate according to aconventional technique was compared with that according to the presentinvention. As a result, formation of interference fringes was observedin the conventional technique, but formation of interference fringes wasnot observed in the present invention. This indicates thatirregularities on a scale comparable with light wavelength were formedat the contact plane due to the low affinity between silica glass andpolyether ether ketone resin according to a conventional technique;however, such irregularities disappeared because of the improvedaffinity between the substrates according to the present invention. Whenshear stress was applied to a region between the substrates, a higheryield stress was exhibited by the present invention than by theconventional technique. In addition, the adhesion plane between thesilica glass plate and the polyether ether ketone resin plate was brokenaccording to the conventional technique; however, a silica glass bulkbody was broken instead of the adhesion plane according to the presentinvention. The results indicate that the adhesion strength is notimproved as a result of pressure bonding, but rather that it is improvedby chemical bonding and anchor effects.

Table 1 shows pressure resistance of the composite structure determinedwhen various conditions for dehydrating the hydrolyzable siliconcompound after it had modified the silica glass surface were examined.

TABLE 1 Dehydration conditions Pressure resistance 150° C., 20 minutes x(<0.1 MPa) 150° C., 10 minutes Δ (5 MPa) 150° C., 1 minute ∘ (≥20 MPa) 28° C., 24 hours ∘ (≥20 MPa)  28° C., 4 hours ∘ (≥20 MPa)  28° C., 1minute ∘ (≥20 MPa)

Table 1 demonstrates that pressure resistance tends to decrease as thedehydration temperature is increased and the period of dehydration isprolonged. It is considered that such results are attained becausehydrolysis of the hydrolyzable silicon compound advances more as thedehydration temperature is increased and the period of dehydration isprolonged, and the frequency for chemical bonding thereof to thepolyether ether ketone resin lowers. Thus, the effects of the presentinvention are understood as being derived from adhesion strength that isimproved via chemical bonding. Accordingly, the period during which thehydrolyzable silicon compound is allowed to stand after it is applied tothe silica glass substrate surface and the remaining solvent is allowedto evaporate is preferably shorter.

Hereafter, the experimental examples verifying the effects according tothe present invention are examined.

A polyether ether ketone resin tubing having an inner diameter of 0.7mm, an outer diameter of 1.6 mm, and a length of 100 mm and a silicaglass tubing having an inner diameter of 0.5 mm, an outer diameter of0.6 mm, and a length of 100 mm were prepared. With the use of anisopropanol solution comprising 1% by weight of 1,000- to 2,000-mers oftetraethoxysilane dissolved therein, a silica glass surface was modifiedwith a hydrolyzable silicon compound via dip coating. Thereafter, asshown in FIG. 1 and FIG. 2, the silica glass tubing was inserted to adepth of 10 mm into a polyether ether ketone resin tubing, an area inthe vicinity of a contact region between the silica glass tubing and thepolyether ether ketone resin tubing was heated to 400° C. using aheating wire in a shape capable of covering the contact plane, and theresultant was naturally cooled to room temperature to produce acomposite tubing. For the purpose of comparison, a composite tubing inwhich tubings were adhered to each other was produced in the manner asdescribed above while refraining from using the hydrolyzable siliconcompound in accordance with a conventional technique. When meltingpolyether ether ketone resin, two tubings were subjected to thermalpressure bonding using a circular metal plate made of stainless steel.

For the pressure resistance test, a pump capable of delivering liquid ata high pressure, such as a pump 2101 for a liquid chromatographyapparatus, and an acetonitrile solution were prepared, and theexperimentation system shown in FIG. 21 was connected. A tubing 2102, acomposite body 2103 provided with a flow channel, and a tubing 2104 forpressure application are connected to the pump 2101. A stainless steeltubing with an inner diameter of 1 mm was used as the tubing 2102, sothat the pressure could be suppressed to an ignorable level, and astainless steel tubing with an inner diameter of 0.1 mm was used as thetubing 2104, so that pressure could be applied thereto. The liquiddelivery pressure at which liquid leakage occurs was designated as thepressure resistance level, and the conventional technique was comparedwith the present invention. As a result, as shown in FIG. 22, liquidleakage was observed at a liquid delivery pressure of 6 MPa on averageaccording to the conventional technique, and liquid leakage was observedat a liquid delivery pressure of 25 MPa on average according to thepresent invention. Thus, significant improvement in pressure resistanceaccording to the present invention was confirmed. According to thepresent invention, a fissure was generated in the bulk body of thepolyether ether ketone resin tubing instead of the plane on which twotubings were bonded to each other, and liquid leakage occurred therein.Such results also verify the improved adhesion strength because ofchemical bonding and anchor effects.

As another embodiment, two silica glass window materials with a diameterof 10 mm and a cell body made of polyether ether ketone resin providedwith a hole for a flow channel with a diameter of 0.5 mm and a hole foran optical path with a diameter of 0.9 mm and a length of 10 mm wereprepared, and the window materials were modified with a hydrolyzablesilicon compound with the isopropanol solution via dip coating.Thereafter, the cell body was sandwiched with the window materials, thecontact planes between the cell body and the window materials wereheated to 400° C. through the window material using plates heated to400° C., and the resultant was naturally cooled to room temperature. Atubing with an inner diameter of 0.1 mm comprising a glass capillarycoated with polyether ether ketone resin was provided at the inlet andthe outlet of the flow channel of the cell body, and an area in thevicinity of the cell body and the tubing was heated to 400° C. using aheating wire in a shape capable of covering the contact planes.Thereafter, the resultant was naturally cooled to room temperature so asto produce a flow cell shown in FIG. 11. For a comparison, a flow cellshown in FIG. 11 was produced using a cell body with dimensions and aconfiguration identical to those of the cell body described above, whichis made of stainless steel, by subjecting the window materials and thecell body to a mechanical fastening system according to a conventionaltechnique involving the use of 12 components, such as ferrules, nuts,and O rings.

As a result of the pressure resistance test performed using theexperimental system shown in FIG. 21, pressure resistance according tothe conventional technique was found to be 12 MPa on average, andpressure resistance according to the present invention was found to be25 MPa on average. Thus, the improvements in terms of the number ofcomponents reduced and pressure resistance according to the presentinvention were confirmed.

As a further embodiment, a cell body comprising a silica glass capillaryhaving an inner diameter of 0.1 mm, an outer diameter of 0.35 mm, and alength of 3 mm, a two-way joint made of polyether ether ketone resinprovided with a 0.4-mm hole for a flow channel, and a tubing having aninner diameter of 0.1 mm composed of a glass capillary coated withpolyether ether ketone resin were prepared. The cell body surface wasmodified with the isopropanol solution. Thereafter, the cell body, thetwo-way joint, and the tubing were positioned as shown in FIG. 12, andheating wires capable of covering the contact planes were positioned inthe vicinities of the regions in which the components described abovewere connected to each other, so as to heat the structure to 400° C. Thestructure was naturally cooled to room temperature to produce a flowcell shown in FIG. 12. For a comparison, a flow cell was produced in themanner as described above while refraining from using a hydrolyzablesilicon compound in accordance with a conventional technique. As a flowcell shown in FIG. 15, also, a cell body comprising a silica glasscapillary having an inner diameter of 0.5 mm, an outer diameter of 0.6mm, and a length of 10 mm, a quartz optical fiber having a core diameterof 0.4 mm, a clad diameter of 0.44 mm, and a length of 45 mm, athree-way joint made of polyether ether ketone resin provided with a0.7-mm hole for a flow channel, and a commercially available tubinghaving an inner diameter of 0.1 mm composed of a polyimide-coated glasscapillary coated with polyether ether ketone resin were prepared, andthe cell body surface and the optical fiber surface were modified withthe isopropanol solution. Thereafter, the cell body, the optical fiber,the three-way joint, and the tubing were positioned as shown in FIG. 15,and heating wires capable of covering the contact planes were positionedin the vicinities of the regions in which the components described abovewere connected to each other, so as to heat the structure to 400° C. Thestructure was naturally cooled to room temperature to produce a flowcell shown in FIG. 15. For a comparison, a flow cell was produced in themanner as described above while refraining from using a hydrolyzablesilicon compound in accordance with a conventional technique.

As a result of the pressure resistance test of the flow cell, pressureresistance of the flow cell according to the conventional technique wasfound to be 5 MPa on average, and pressure resistance of the flow cellaccording to the present invention was found to be 25 MPa on average. Atthe end of the region in which the three-way joint is connected to theoptical fiber in the flow cell according to the present invention, asshown in FIG. 23, a configuration such that the polyether ether ketoneresin wets the silica glass, and more specifically, a configuration suchthat the polyether ether ketone resin forms a convex configuration withrespect to the quartz optical fibers, was observed.

Finally, embodiments of a flow cell for a microchip are described. Twosilica glass plates (thickness: 1 mm; 5 mm×5 mm) were prepared, and oneof the silica glass plates was provided with two 0.5-mm holes at aninterval of 2 mm. The polyether ether ketone resin plate (thickness: 1mm; 5 mm×5 mm) was provided with a hole for a flow channel (0.5 mm×2mm). After the silica glass plates were modified with the hydrolyzablesilicon compound using the isopropanol solution, the polyether etherketone resin plate was sandwiched with the silica glass plates, thesilica glass plates were further sandwiched with the plates heated to400° C., and the areas of contact between the silica glass and thepolyether ether ketone resin were heated to 400° C. After the structurehad naturally cooled to room temperature, a tubing with an innerdiameter of 0.5 mm composed of a glass capillary coated with polyetherether ketone resin was positioned within a hole provided on the silicaglass. The structure was heated to 400° C. using a heating wire and thennaturally cooled to room temperature to produce a flow cell shown inFIG. 19. For a comparison, a flow cell in the same configuration wasproduced using commercially available pressure bonding components.

As a result of the pressure resistance test performed using theexperimental system shown in FIG. 21, pressure resistance according tothe conventional technique was found to be 3 MPa on average, andpressure resistance according to the present invention was found to be23 MPa on average. Thus, the present invention is effective for a flowcell for a microchip.

In the embodiments described above, it was confirmed that pressureresistance attained via electromagnetic induction heating would besubstantially the same as that attained via electrical heating.

It should be noted that the present invention is not limited to theembodiments described above and various modifications thereof are withinthe scope of the present invention. For example, the embodiments aboveare described in detail to clearly explain the present invention, andthe present invention is not limited to embodiments comprising all theconstituents described herein. A part of a constitution according to aparticular embodiment can be replaced with a constitution according toanother embodiment, and a constitution according to a particularembodiment can be added to a constitution according to anotherembodiment. In addition, a part of a constitution according to anembodiment can be modified with another constitution through addition,deletion, or replacement.

DESCRIPTION OF NUMERAL REFERENCES

-   301: First cylindrical tube-   302: Second cylindrical tube-   801, 1201, 1401, 1501: Cell body-   802, 803: Window material-   804, 1204, 1205, 1404, 1405, 1504, 1505, 1705, 1906: Flow channel-   805, 1208, 1510, 1706, 1907: Hydrolyzable silicon compound-   806, 807: Heating plate-   808, 809, 1206, 1207, 1406, 1407, 1506, 1507, 1703, 1704, 1904,    1905: Tubing-   1202, 1203, 1401, 1402: Two-way joint-   1502, 1503: Three-way joint-   1508, 1509: Optical fiber-   1701, 1901, 1902: Silica glass substrate-   1702, 1903: Resin substrate

The invention claimed is:
 1. A flow cell for a liquid analyzer,comprising: a glass substrate, a hydrolyzed silicon compound modifying aglass substrate surface of the glass substrate, and a resin substrate,wherein the glass substrate surface is in contact with a resin substratesurface of the resin substrate, and the glass substrate is adhered tothe resin substrate via chemical bonding and anchor effects via thehydrolyzed silicon compound, and wherein the resin substrate ispolyether ether ketone resin, polyphenylene sulfide resin, or polyamideresin.
 2. The flow cell according to claim 1, wherein the glasssubstrate is synthetic silica glass, fused-silica glass, borosilicateglass, or soda glass.
 3. The flow cell according to claim 1, wherein aflow channel is disposed in the resin substrate.